1. Field of Invention
The present invention relates to a method for synthesizing 4,4-dihalogen-2-(dialkylamino)methylene-3-oxy-alkyl butyrate and its derivatives, and more particularly to a method using molecular sieves to remove water and adsorb chloride of hydrochloric acid for a removal of chloride to avoid generating by-product, so yield of product can be increased.
2. Description of the Related Art
4,4-dichloro-2-(dimethylamino)methylene-3-oxy-ethylbutyrate (DDMOEB) and its derivatives are an intermediate with halogen and multiple functional groups. Because the functional groups are able to modify molecules during an organic synthesis, DDMOEB and its derivatives are suitable for synthesizing active intermediates of medicine or agricultural chemicals such as insecticide. Therefore, DDMOEB and its derivatives play important roles in medicine and agricultural fields.
U.S. Pat. No. 2,987,491, U.S. Pat. No. 4,027,037, U.S. Pat. No. 4,046,803, U.S. Pat. No. 4,319,024, U.S. Pat. No. 4,723,031, U.S. Pat. No. 4,772,711, US2006/0252944A1, DE 2,938,872, DE 3,037,086, CA 0,728,187 and EP 1,000,926 A1, disclose methods for synthesizing DDMOEB and its derivatives. These conventional syntheses use inorganic alkaline water, primary and secondary amine or other organic alkaline compounds at −20° C. to 30° C., and then require complicated and time-consuming purification to obtain the product. Overall, these conventional methods have the following shortcomings:
(1) Raw material for the synthesis is 2,2-dichloroacetyl chloride and its derivatives have an α-hydrogen. Therefore, if conditions of the synthesis are not controlled well, the synthesis produces multiple by-products. Therefore, a yield of DDMOEB and its derivatives is reduced (yield: 20% to 40%) (EP 1,000,926 A1 and Journal of Organic Chemistry 1968, vol. 33, p. 816).
(2) Synthesis is in a two-phase system, so reaction between two phases does not reach completion.
(3) Hydrochloric acid is generated from the organic alkaline compound during synthesis, which leads to a competing polymerization reaction rather than synthesizes product (Journal of Organic Chemistry 1968, vol. 33, p. 816).
(4) The synthesis produces water, which makes the synthesis complex.
(5) Temperature is hard to control because the temperature is increased from −20° C. to 50° C. during synthesis.
(6) After synthesis, a crude product undergoes purification. However, the crude product is in an emulsion so is difficult to purify, therefore the purification takes time and easily generates by-product to further decrease the yield of DDMOEB and its derivatives.
(7) A lot of organic solvent is used during purification, which contaminates the environment.
The conventional methods are inefficient with low yields, so DDMOEB produced by the conventional methods is expensive and so is not good for industry. To overcome the shortcomings, the present invention provides a method for synthesizing DDMOEB and its derivatives to mitigate or obviate the aforementioned.
Chemistry Communications 1997, p. 281-282, Journal of Organic Chemistry 1986, vol. 51, p. 1922, Chemistry Letter 1986, p. 1967-1968, and Journal of the American Chemical Society 1989, vol. 111, p. 1940 disclose a property of sodium calcium aluminosilicate to remove water efficiently and prevents accumulation of hydrochloric acid by removal of chloride. Therefore, the inventor utilizes properties of sodium calcium aluminosilicate to synthesize 4,4-dihalogen-2-(dialkylamino)methylene-3-oxy-alkylbutyrate and its derivatives.